[0.16 stock] Falcon 9 (satelite launcher) and Falcon Heavy (Minmus + Moon trip)

[Caroliano]

So, I tried to replicate the rockets from SpaceX in KSP. In this post, I will talk about the Falcon 9, and in the next the Falcon Heavy.

For more info about it: http://en.wikipedia.org/wiki/Falcon_9

It uses 9 identical engines in the first stage, with quite a bit of thrust, but relatively low efficiency: at sea level, each Merlin 1C engine has 560 kN of thrust, and a Isp of 300s. The large LV-T30 Liquid Fuel Engine is then used because it's 1200kN of thrust and 280s~330s Isp. As the thrust is lower, our rocket will be smaller than the real one, but has an higher ratio of take-off weight/payload, probably because Kerbal is much smaller than Earth.

For the second and last stage, the real Falcon 9 uses a Merlin 1C engine optimized for vacuum, with 411kN of thrust and 342s of Isp. As the large LV-909 Liquid Fuel Engine is pathetically bad, I chose to use the much lighter and higher thrust LV-T30 small, that has Isp of 370s on vacuum, and 215kN of thrust. This higher thrust is especially desirable while the time warp is limited in low altitudes.

The all SpaceX rockets use the same fuel tank for all stages, variating only the height, in order to generate scale economics and drive the cost down. This is why they use so many identical engines in a rocket too. I tried to reproduce it here, but KSP don't have this concept, and the Kerbal Space Program is already working with a limited set of parts anyway.

So, how it works?

This was using mechjeb ascent autopilot, but you can do better manually. Note that at the end of the stage 1 acceleration, the G-forces reach 3+Gs, and it can torn appart the craft. I recommend to throttle down the engine in the last half of the last fuel tank. I'm using the large decoupler fix, that increases it's strength 8 fold, so this didn't happened in those fights. I used some struts anyway. The real Falcon 9 turns off 2 engines at about the same time in the ascent (they can't throttle down).

In the real Falcon 9, about 30 minutes after deploying the payload, the last stage slows down itself to re-enter in the earth atmosphere. Unfortunately, we can't program this in KSP yet, so it will leave debris in orbit even though it has enough delta-v to not let it happen...

So, here is the .craft file:

http://www./download.php?unxdqjjqgbded26

No mods included. I removed the mechjeb and KSP engineer before uploading it.

[Caroliano]

The Falcon Heavy is kinda 2 Falcon 9 first stages stacked on the side of an bigger Falcon 9 one as boosters, with fuel cross-feed to keep the central one full and firing. This makes it more fuel efficient than Falcon 9, and capable of lifting heavier payloads further. But it isn't reality yet: the first launch is planned for 2013.

More information: http://www.spacex.com/falcon_heavy.php

For the lander, I used four little LV-909 engines instead of a big one, because they have half of the weight, higher Isp, and sufficient combined thrust. It also helped in the integrity of the craft during takeoff, and to give a wider base for the lander legs, to improve stability. One can use 6 or 8 of those modules for more autonomy.

My falcon heavy can carry quite heavy Mun/Minmus landers. One can still add one more big tank of fuel to each lateral booster to increase a little the payload it can lift. It is totally DEBRIS FREE. The first stage, after dropping the boosters, carry the ship to almost a full Kerbal Orbit. The second stage can be used for a Trans-Munar injection, and there will still be fuel for some slow down when we reach there.

In fact, I made a whole Kerbal -> Minmus -> Mun -> Kerbal trip using this craft, and even landed on minmus on top of the second stage! I avoided as much as possible the fuel bug, and even wasted some fuel going awkwardly to full thrust in landing. I only used mechjeb for the ascent (to colect the data, not because it is more efficient), and for the injection to minmus orbit. From there I only used the data it provided and the stock ASAS. I landed carefully, and messed up in the trip from minmus to the mun, but still managed to come back to kerbal!

See the whole trip here (I can comment more on it if requested): http://imgur.com/a/SZR4q#0

And, of course, the .craft file:

http://www./download.php?hf4331gubt26d4t

Edited August 14, 2012 by Caroliano

[Saganist]

Great job man!